Conventionally, a drug for injection (injection or drug solution) is supplied in a container with its mouth portion sealed with a rubber closure, and upon administration, a hypodermic needle is inserted through the rubber closure to collect the drug solution into a syringe from the container. Containers of the above-described type are called “vials” and are used widely. Rubber closures for use in such vials include those provided with a substantially cylindrical leg portion arranged on a lower wall of a head portion and those not provided with such a leg portion. In the case of a rubber closure provided with no leg portion, it cannot seal a container by itself because it is in the form of a thin flat disc. The sealing of the container is, therefore, effected by assembling the rubber closure in a protector and capping the container with the protector (see, for example, JP-A-11-035062).
With a rubber closure provided with a leg portion, on the other hand, sealing is generally achieved by inserting the leg portion into a mouth of a container, said mouth being a drug-solution-filling neck portion, and then wrapping up a circumferential side wall portion of the rubber closure and a flange portion of the container with an aluminum or plastics cap. FIG. 8A illustrates a container (vial) with a drug solution contained in a state sealed by a conventionally-known rubber closure having a leg portion and inserted in a mouth portion, i.e., a drug-solution-filling neck portion of the container. FIG. 8A shows a drug-solution-containing portion 1, the drug-solution-filling neck portion 2, and the drug solution L such as an injection contained in the drug-solution-containing portion. Designated at numeral 3 is the rubber closure for sealing the drug-solution-filling neck portion 2. By inserting a leg portion of the rubber closure 3 into the mouth portion 2 of the container, the drug-solution-filling neck portion 2 is sealed up. Therefore, the rubber closure generally has a substantially cylindrical shape so that, as illustrated in FIG. 8A, its outer circumferential wall can be brought into close contact with the inner circumferential wall of the drug-solution-filling neck portion 2 of the container (see, for example, JP-A-08-275984, JP-A-2002-017816, and JP-A-10-179688).
An inner wall of the drug-solution-filling neck portion 2 of the conventional container (vial) is, however, not provided with any concave or convex portion. In the state that the container is capped with the rubber closure, a lower end wall 7 of the leg portion 10 of the rubber closure is, therefore, exposed to the interior space of the drug-solution-containing portion 1 as shown in FIG. 8A. According to an investigation conducted by the present inventors, a drug solution 18 may remain on or in the vicinity of the lower end wall 7 of the leg portion 10 of the rubber closure as depicted in FIG. 8B when the container with the drug solution contained in a state sealed with the rubber closure 3 having the leg portion is turned upside down and the drug solution is collected by a syringe through the rubber closure 3 positioned on the lower side. JP-A-2002-017816 cited above proposes a container constructed such that an interior space in a bottom part of the container takes the form of a circular cone to permit withdrawing a drug solution by a syringe from the container without tilting the container. According to an investigation conducted by the present inventors, however, the drug solution 18 may also remain on or in the vicinity of the lower end wall 7 of the leg portion 10 of the rubber closure depending on the kind of the drug solution. There is, accordingly, a room for improvements.
A drug solution for injection, because of its property, effect or function, must be properly collected from a container and must be administered at an accurate dose. Nonetheless, the drug-solution-containing portion of a vial tends to have a smaller capacity in recent years, so that the remaining of the drug solution in the container after its collection by a syringe causes a greater problem than the case of a vial having a drug-solution-containing portion of large capacity. As a measure for such a problem, it may be contemplated to fill a drug solution while taking into consideration an amount in which the drug solution is to remain in the container. This method, however, accepts the wasting of the drug solution as a premise, and is not preferred from the standpoint of effective utilization of a resource and further, from the standpoint of disposal or the like of a waste material. On the other hand, drug solutions include expensive ones. In recent years, very expensive drug solutions as costly as from several thousands yen to several tens of thousands yen have been put on the market. It is, therefore, not only a matter of wasting but also forcing a patient to bear a high expense that such a costly drug solution remains in a container and is discarded.